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Structure of EspB from the ESX-1 type VII secretion system and insights into its export mechanism

Matthew Solomonson1, Dheva Setiaputra2, Karl A T Makepeace3

  • 1Department of Biochemistry and Molecular Biology, Life Sciences Centre, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada; Centre for Blood Research, Life Sciences Centre, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada.

Structure (London, England : 1993)
|February 17, 2015
PubMed

Insights

Mycobacterium tuberculosis (Mtb) uses the ESX-1 secretion system to infect macrophages. Researchers determined the structure of EspB, revealing a heptameric pore structure essential for virulence.

Area of Science:

  • Microbiology
  • Structural Biology
  • Cell Biology

Background:

  • Mycobacterium tuberculosis (Mtb) infection relies on the ESX-1 secretion system to deliver virulence factors.
  • The ESX-1 system exports proteins across the Mtb cell wall, aiding macrophage invasion and spread.
  • The structure and function of secreted ESX-1 proteins, like EspB, are largely unknown.

Purpose of the Study:

  • To elucidate the structural basis of EspB function within the ESX-1 secretion system.
  • To understand how EspB contributes to Mtb's virulence and host cell manipulation.

Main Methods:

  • X-ray crystallography was used to determine the high-resolution structure of EspB.
  • Electron microscopy provided insights into the oligomeric assembly of EspB.
  • Biochemical analyses investigated EspB interactions and potential pore formation.

Main Results:

  • EspB adopts a PE/PPE-like fold and forms heptameric oligomers.
  • The oligomeric EspB structure creates a barrel-shaped complex with a central pore.
  • Structural data revealed interactions within EspB's bipartite secretion signal sequence, forming an aromatic surface.

Conclusions:

  • EspB oligomerization into a pore-forming structure is critical for its role in Mtb virulence.
  • The findings offer insights into the secretion mechanism and function of ESX-1 virulence factors.
  • This study provides a structural foundation for understanding Mtb pathogenesis and developing targeted therapies.

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